1. Field of the invention
The present invention relates to image formation cartridges for an image forming apparatus, such as an ink-jet printer. The image formation cartridge typically includes an image formation sheet and an ink apply roller for applying ink fed from an ink tank to the image formation sheet. The present invention also relates to an image forming apparatus employing such an image formation cartridge.
2. Description of the prior art
Ink-jet printers are known as one type of nonimpact printer. The ink-jet printer includes a thermal head and an ink permeable sheet having a large number of small holes. The ink permeable sheet on which ink is applied from an ink tank reciprocates over the head. When the small holes filled with ink have reached the thermal head, the thermal head is energized to be heated quickly in accordance with an image signal. Then ink droplets, corresponding to the holes opposite to the thermal head, are ejected from the ink permeable sheet, thus printing a visible image on a recording sheet.
One example of an ink supply system is shown in U.S. Pat. No. 4,608,577, issued on Aug. 26, 1986 in the name of Ken-ichi Hori, and entitled INK-BELT BUBBLE PROPULSION PRINTER. In this prior art, an endless film 1 is extended between a thermal head member 4 and one end portion of an ink supplying sponge roller 16, as shown in FIG. 7. The other end portion of roller 16 is soaked in ink stored in an ink tank 7. The ink in ink tank 7 is sucked up by roller 16, and is filled or applied to the holes or recess portions of film 1, which contact and pass the surface of roller 16. The ink stored in tank 7 may be supplied to film 1 through sponge roller 16. However, in this system, nonuniformity of the ink supply may occur between one end portion and the other end portion of the sponge roller 16. In particular, it is difficult to uniformly supply the ink to the entire portion of the roller 16 if this system is applied to a line printer type ink-jet printer. This is because an elongated roller is needed to supply ink to the film, and thus the ink may not be sucked uniformly from one end portion to the other end portion of the roller. Therefore, a high printing quality may not be achieved in a line printer using the conventional system.